Flexible armoured telephone cords

ABSTRACT

A flexible armoured cord, as used in pay telephone units, is given an epoxy-resin coating, preferably by a fluid bed process. A very thin uniform coating is applied and averts wear and damage to the telephone unit housing without reducing flexibility of the cord. The coating is extremely abrasion resistant.

D United States Patent 1191 1111 3,803,344 Hemming et al. Apr. 9, 1974 FLEXIBLE ARMOURED TELEPHONE 2,409,530 10/1946 Bennett 174/109 x CORDS 3,334,177 8/1967 Martin 174 108 x 3,552,445 1/1971 Andrews 138/144 lnventorsi Raymond Charles Flemming; Joseph 2,120,088 6/1938 Carlson 174/109 Thompson; Henry Allan Main, allof London, Ontario, Canada FOREIGN PATENTS OR APPLICATIONS [73] Assignees: Northern Electric Company Limited, 3,917 2/1910 Great Britain 174/ 109 Montreal Quebec Canada; aid 677,212 5/1939 Germany 1 174/109 H i and Thompson; 1,165,045 9/1969 Great Bntam 174/110 E Bell-Northern Research Ltd., a i Ontario Canada; by Sald Primary Examiner-Bernard A. Gilheany am Assistant ExaminerA. T. Grimley [22] Filed: Apr. 9, 1973 Attorney, Agent, or Firm-Sidney T. Jelly 21] Appl. 190.; 349,319

57 ABSTRACT [52] U.S. Cl. 174/109, 174/107 1 [51] Int. Cl. H011) 7/22 A flexible armoured Cord as used in pay telephone [58] Fleldof Search 174/102 R, 102 D, 107, units is given an epoxyqesin coating, preferably by a 174/ 110 fluid bed process. A very thin uniform coating is ap- 17411136 145 plied and averts wear and damage to the telephone unit housing without reducing flexibility of the cord. [56] References C'ted The coating is extremely abrasion resistant,

UNITED STATES PATENTS 7 2,303,281 11/1942 Johnson 174/109 1 Claim, 2 Drawing Figures PATENIEDAPR 9 an l FLEXIBLE ARMOURED TELEPHONE CORDS This invention relates to flexible armoured telephone cords, particularly the cords which connect the headset to the wall unit or the like in pay telephones and similar public use telephones.

It is necessary to armour the flexible cord connecting the headset to the wall unit to prevent damage to the cord, either deliberate or accidental or through wear. However the armour covering causes wear problems on the wall unit. Rubbing of the armoured cord against the cover of the wall unit scratches the cover and scrapes off the paint.

Attempts have been made to prevent this wear on the wall unit, as by covering the armour with a flexible plastic coating. However it has been found that such coatings reduce the flexibility of the cord. A minimum degree of flexibility is determined by the comfortable use of the headset, and any restriction on flexibility must be overcome by increasing the length of the cord which is expensive and often inconvenient in that the cord becomes cumbersome.

The present invention provides a flexible armoured cord which has an epoxy-resin coating, preferably applied by a fluidized bed process. The cord retains its flexibility, does not damage the wall unit and the coating is extremely wear resistant.

The invention will be understood by the following description in conjunction with the accompanying drawings, in which:

FIG. 1 is a view of a flexible armoured cord, and

FIG. 2 is a cross-section on the line ill-ll of FIG. 1 to an enlarged scale.

FIG. 1 illustrates a flexible armoured cord comprising central electrically conducting cord and an outer flexible metallic sheath 11. In use the sheath is attached at each end to a part of the telephone unit, one end to the wall or panel unit and the other end to the headset. The ends of the sheath are enclosed in end caps 12.

The invention is seen more clearly in FIG. 2 which is to a considerably larger scale. The metallic sheath 11 is formed from a spiral of metal in the conventional way having a double channel formation 13 and 14 one channel facing the interior and one channel facing to the exterior of the sheath. The end flange 15 of channel 13 overlaps the end flange 16 of channel 14. There are slight clearances 17 between the edges of the flanges 15 and 16 and the channel bases. The end flanges 15 can move axially in the channels 14 as can also the end flanges 16 in the channels 13. This permits flexing of the sheath in the known manner.

The sheath is given a thin coating 17 of a synthetic resin. Preferably the resin is applied by a fluidized bed process, this providing a thin, even coating. The resin is preferably an epoxy resin although other resins can be used with appropriate processes. The coating 17 is very thin, but does not pass into the interior of the sheath. The coating extends over the edges of the flanges l5 and 16. The thin coating does not reduce the flexibility of the sheath, which is unexpected, and an increase in flexibility has been obtained. It is believed that increased flexibility may arise from the resin coating the edges of the flanges and thus preventing a raw metallic edge rubbing on the coating in the channels.

Generally a clear coating is applied, in which case the armoured cord has the same appearance as conventional cords. Alternatively coloured coatings can be applied giving a new appearance to the cords not hitherto economically possible. Cords can be provided with a coloured coating to match handset and/or telephone unit.

Although very thin of the order of 0.005 inches the resin coating is extremely resistant to abrasion itself and also prevents abrasion of the telephone unit cover.

What is claimed is:

1. A flexible armoured telephone cord including a central insulated electrically conducting cord and an outer flexible metallic sheath, the metallic sheath comprising a spiral wound length of metal, the transverse cross-section of the length of metal of double channel formation and comprising a first channel having its interior facing inwards towards the central cord and a second channel having its interior facing outwards from the sheath, the two channels having a common flange, each channel having an end flange and a connecting base part connecting the relative end flange to the common flange, an end flange of said first channel on one spiral turn in overlapping relationship with the end flange of said second channel of a preceding spiral and having an inner edge spaced a small distance from the adjacent connecting base part; and a thin coating of synthetic resin on the outside of the sheath, the coating extending over and adhering to the end flange and connecting base part of said first channel, the said common flange and the connecting base part only of said second channel, the coating extending spirally along the metal sheath, and of a thickness less than said small distance between said inner edge and said adjacent connecting base part. 

1. A flexible armoured telephone cord including a central insulated electrically conducting cord and an outer flexible metallic sheath, the metallic sheath comprising a spiral wound length of metal, the transverse cross-section of the length of metal of double channel formation and comprising a first channel having its interior facing inwards towards the central cord and a second channel having its interior facing outwards from the sheath, the two channels having a common flange, each channel having an end flange and a connecting base part connecting the relative end flange to the common flange, an end flange of said first channel on one spiral turn in overlapping relationship with the end flange of said second channel of a preceding spiral and having an inner edge spaced a small distance from the adjacent connecting base part; and a thin coating of synthetic resin on the outside of the sheath, the coating extending over and adhering to the end flange and connecting base part of said first channel, the said common flange and the connecting base part only of said second channel, the coating extending spirally along the metal sheath, and of a thickness less than said small distance between said inner edge and said adjacent connecting base part. 